Naming of Virtual Machines

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(This feature is currently provided on the cvs version)

User perspective

Umview suite provides a new command vuname. vuname(1) is an extension of uname including three more fields:

  • serverid: the pid of the umview process.
  • viewid: the number of subview managed by the same server.
  • viewname: the name of this view (when defined by viewname(1) or with umview option -V).

vuname behaves as uname when run outside an umview machine.

$ vuname -a
Linux myhostname 2.6.22-viewos #4 SMP Mon Jul 23 11:14:06 CEST 2007 i686 GNU/Linux/View-OS 2123 0
$ viewname virtuous
$ vuname -a
Linux myhostname 2.6.22-viewos #4 SMP Mon Jul 23 11:14:06 CEST 2007 i686 GNU/Linux/View-OS 2123 0 virtuous

viewname(1) provides also an id for the view for the shell prompt. For example, this .bashrc file provides a prompt with an id for the umview machine (and just the hostname when a bash run outside umview).

$ cat ~/.bashrc
....
if [ -x /usr/local/bin/viewname ]; then
  viewname=$(/usr/local/bin/viewname -pq)
fi
if [ "$viewname" == "" ]; then
  viewname=$(/bin/hostname)
fi

PS1='${debian_chroot:+($debian_chroot)}\u@$viewname:\w\$
....

With this definition the prompt for a process running outside the virtual machine is:

username@myhostname:~$

Starting a virtual machine without the -V option:

username@myhostname[2123:0]:~$

And with the -V virtuous option:

username@virtuous:~$

Using these commands it is possible to have a feedback about which view a process runs into. They are like a compass to avoid to get lost in the view space.

Programmer Perspective

The libumlib library provides the following call:

int um_view_getinfo(struct viewinfo *info);

where struct viewinfo is an extension of struct utsname provided by uname(1).

struct viewinfo { 
  struct utsname uname;
  pid_t serverid;
  viewid_t viewid;
  char viewname[_UTSNAME_LENGTH];
};

The pair of values serverid/viewid can be used as unique id of a view (running on the same host).

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